Core Unit B will provide expertise and technical support for the analysis and sorting of cells by flow cytometry. The unit will interact with the investigators of the SCOR projects to study the onset and regulation of the expression of blood group antigens, mechanisms of hemopoietic deficiencies related to the antigens , and to enumerate and purify subpopulations of cells and cell lines with relevant features. For these purposes Core Unit B will provide the following specific technical support to the projects: - The Rh Project: Analysis and selection of transfected cells. Analysis and sorting of subpopulations of bone marrow and cord blood for expression studies during early erythroid differentiation. Analysis of Rhced and Rhag mutated mice by flow cytometry and cell sorting to assist in studies on the knockout phenotype. -The Kell Project: Analysis and sorting of subpopulations of bone marrow and cord blood for expression studies in the stem cell compartment and to assist in clarifying the nature of Kell related anemia. Analysis of hemopoietic cells from KELL and XK knockout mice and their offspring by flow cytometry and cell sorting to assist in studies to determine the knockout phenotype. - The Malaria Project: Analysis and sorting of transfected cells for binding-ligands and receptors for malaria. Comparisons of infections of cells by malaria parasites using untreated versus biotinylated red blood cells. Analysis and sorting of reticulocytes for the isolation and characterization of an additional Malaria vivax parasite receptor. - The Clinical Immunohematology Project: Analysis and screening of manipulated cells for the expression of blood group antigens and testing of newly developed antibodies with regard to their specificity for blood group antigens. Core Unit B consists of a team of experienced flow cytometry and cell sorter specialists. All necessary equipment is available.